Radio apparatus for determining distance and direction



March 21, 1939. H E. HOLLMANN 2,151,323

RADIO APPARATUS FOR DETERMINING DISTANCE AND DIRECTION Filed May 25, 1956' I Indicator Re lected/ ,2 ave Recs Ever 5 Tmuwmimr n v wwxm HANS ERICH HOLLMANN ATTO R N EY Patented 21, IQBQ lie-siren stares rarest err-res RAHKG APPARATUS FOR DETERMINKNG DHSTANCIE AND DKRECTIUN Hans Erich Hollmann, Berlin, Germany, asslgnor to Telefunhen Gesellschalt fliir Drahtlose Telegraphic m. l). R, Berlin, Germany, a corporation oil Germany Application May 23, 1936, Serial No. 81,357

' Kn Germany May 18, 1935 2 Claims. (011. 250-1) This invention relates to apparatus and a this case, the number of nodes can be determined method for measuring distance and for indicating with by far greater accuracy, since in' the first. direction by means of ultra-short waves. The inplace the number of waves contained in a given ventl'on may be used as an altimeter as well as distance is much smaller. Hence there are fewer a for horizontal measurements of distance. nodes than when shorter waves are used; Sec- 5 In order to determine the distance between ondly, lower frequencies can be measured with a reflecting object or a reflecting surface and. a much greater accuracy than would be possible in transmitter sending out electrical waves, various the ultrashort wave range. methods v n v p Principally the The application of the idea of the invention in methods are based upon the fact that standing will now be further explained with reference to a lo waves of the radiated carrier oscillations are propractical example shown in the drawing. The duced between transmitter and place of reflection, embodiment therein shown includes an ultraand which are observed either in a controlling hort wave transmitter S equipped with a\direcreceiver r n e n mi t r p p and wheretional beam radiator. The propagated beam imby through variation of the carrier wave the pinges on the reflecting surface F and is re- 15 num e of 110C165 0f the Sta-riding Waves which flected back to a receiver R adjacent the transmust be known for the distance measurement, itt r, The ultr -short wave transmitter is s ascertained, according to another d, modulated by a second high-frequency generator t e time for P e radiated by the transmitter. G having a constant amplitude but variable and 26) to P s to the Place o reflection and back it exactly adjustable as to frequency. Then, itis as control receiver is meas red. or ompar as r obviously possible .to choose such modulation car Phase w a second pulse d l n to frequencies M that a phase displacement of 180 the receiver from the transmitter across an all? or 360 will be obtained between a, modulation tificial reference base. As high-frequency carill t passing tgwmds F and one t as ri r ultra-Short Waves a ularly suited. ing from F. In the first case, a returning modu- 2,5 sin e th y afi rd he s a p s concentration in lation maximum 1. e. a peak value of the envelthe direction upon the place of reflection, while oping curve of the modulated high-frequency osthey are highly reflected at the same time also cillatipn always coincides with a minimum sent by smaller objects such as airplanes for instance. out, and the two opposite pulses completely'comso In practice, the first-mentioned method becomes pensate each other. In the second case, modula- 30 the more dlflicult, the shorter the wave chosen, tion oscillations of equal phase meet each other since the distance measurement is directly reconsistently so that the sum thereof will be 010- V duced to a wave measurement but according to tained. Whereas in the first case the field the present state of the art'such wave measurestrength is "diminished in the vicinity of the merit cannot be carried out at extremely high ire-' transmitteror at the transmitter proper, in the 35 quencies with the necessary accuracy. Since the second case, a maximum of field strength will be distances to be measured are of the order'of a noted. A reflected wave receiver is accordingly large multiple of the length of ultra-short waves, provided adjacent the transmitter so that these the absolute error in the measurement is great. fluctuations in the fleld intensity can now be ob- 40 The present invention provides means to overserved. Connected with the receiver is an indi- 40 come these difiiculties in that it is based upon the cator which is made responsive to the received teaching that an ultra-short wave modulated with signals. Direct connections are also made hea longer intermediate wave behaves in certain tween the transmitter and the receiver such that respects in such a manner as if only the longer the grid potential applied to a rectifier in the 5 intermediate wave were present, with the exreceiver is under control of the outgoing signals. 5 caption that the conditions of propagation as re- .This provides an unstable adjustment of the rec gards absorption and reflection are those of the tlfler in the receiver,-which, however, produces'a ultra-short carrier wave. .With the present incoordination between the outgoing and incoming ventlon, therefore, all methods of determining signalling energy whereby the occurrence of so vertical distances which hitherto were based upon standing waves may be observed in the indicator.

a Variation of the measuring wave can be ap- To ascertain the distance D, two known modplied to intermediately modulated waves whenulation frequencies M1 and M2 are chosen as limever in place of the carrier frequency, the moduits of gradual variation of the modulation frelation frequency is set in such manner that quency M. Two successive maxima or minima as standing modulation waves" "are produced. in may then be observed. .It is obvious that the phase displacement appearing between the two frequencies M1 and M2 is 360 or a multiple thereof, namely 360 n degrees, where n designates the whole number series. Since the speed of the modulation pulses propagating together with the ultra-short wave carrier, is equal to the speed of light, c, the time difference dt between a modulation pulse emanating from'the transmitter and one returning to the transmitter, will be:

' dt=2 v C Now, if such modulation pulses follow each other continuously, maxima or minima will always be obtained when this time corresponds'to multiples ofthemodulation cycle l/M, therefor:

orwhen introducing M1 and M2:

when assuming that the tuning is adjusted to two I successive mam'ma or minima, then there exists in which we may employ the right hand termof Equation 7 to obtain:

. 2(M2:-M1) (9) Furthermore, in expressing the modulation frequencies M by the modulation waves ;\=c/M there is finally: Y

MM g oe-"M2 But this is the formula obtained when in place of the modulation frequency, the ultra-short wave carrier frequency is directly varied, and the adjustment is carried out to the efiect of producing standing ultra-short waves. Thus, it is proven that by means of the present invention standing modulation waves can in fact be'produced and which as compared with the standing ultra-short waves have theaforementioned prac ltical advantages of a greater accuracy in the measurement. This accuracy may be stillfurther increased if instead of starting with two successive maxima or minima, the different maxima or minima are chosen in accordance with the order number N. The distance D to be determined is then: r

I Whatfis claimed is:

1. The method of measuring the vdistance between a point of emanation of an ultra-high frequency wave modulated by a low frequency wave and a point of reflection of said modulated wave, which comprises, producing an ultra-high frequency carrier wave of fixed frequency and a low frequency wave variable in frequency be-= tween two limiting values, modulating said carrier wave by said low frequency wave, directively transmitting the resulting'modulated carrier wave from said point of emanation to said point of reflection, varying the frequency of the lowfrequency wave between said'two limiting values so as to produce a standing wave as a result of the interaction between. the transmitted wave and the reflected wave, receiving the energy of the standing wave adjacent the point of emanation, indicating the intensity of such energy, and indicating the wavelengths at the two limiting values of the low frequency wave, whereby the distance is indicated as a function of the least common multiple of said wave lengths at the two limiting values.

2. Apparatus for measuring the distance between a point of emanation of an ultra-high frequency wave and a point-of reflection of said wave, comprising means for. generating and transmitting said ultra-high frequency wave, means for modulating said wave with a low frequency wave variable in frequency between two limiting values, means including a receiving circuit adjacent the point of emanation of said modulated wave for combining the directly propagated wave with the reflected wave, an indicator responsive to the energy of the combined waves, and means operative to correlate the observed indicator responses with a measure of the low frequency wave lengths, whereby the said distance I is indicated as a function of the least common multiple of two such wave lengths of said lime itmg values which are observed to produce a maximum indicator response.

HANS ERICH HOLIMANN. 

